These are often the seats near the exit, which, not only have the most leg-room, but are used for people to exit during an emergency.

Quora user Vimal, a frequent flier, revealed this hidden handle that many may not realise exists.

He wrote: “If you notice a small knob near the lever of your tray table, then congratulations, you are sitting in the Overwing Emergency Exit Row,” which he explains is often on smaller planes such as the A320.”

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Plane seats in the evacuation aisles have a handle or knob to prevent the table from being knocked

He continues: “The knob helps to keep the tray table lever from moving into the open position as passengers squeeze between these seats to get to the Overwing Emergency Exit during evacuation.

“It prevents the tray table from opening and blocking the way to the exit. It also serves as a good visual identification and physical identification (when your cabin is dark and filled with thick smoke) for the exit rows.”

Not all seats have this function as they are at less risk of being knocked if passengers are not walking through them.